Spark discharge control means



March 5, 1963 H. c. EARLY 3,080,504

SPARK DISCHARGE CONTROL MEANS Filed March 6,1961

2 Sheets-Sheet 1 INVENTORI 7 \%0Zd a4 ATTORNEYS.

March 5, 1963 H. c. EARLY 3,

' SPARK DISCHARGE CONTROL MEANS Filed March 6, 1961 2 Sheets-Shut 2INVEN TOR.

BY :afay MMM 27M ATTORNEYS.

PARK

Publishing Company, a corporation of Hows Fiied Mar. 6, 1961, tier. No.93,739 12 Claims. (Cl. 315-277) This application relates generally toelectrical control circuits for controlling the discharge of an electricspark and more particularly to new and improved spark dis charge controlcircuits having use with multiple spark electrodes adapted for paralleldischarge channels.

It is known in the prior art, as shown and described in Early et a1.Patent No. 2,737,882, to print or perforate a rapidly moving web or tapeutilizing the energy generated from the discharge of an electric spark.In high speed punching or printing apparatus, for example, a tape is fedbetween a pair of opposed, closely spaced surfaces which confine a spacetherebetween. One surface constitutes a die and the other constitutes ananvil to confine the gases between the tape and surface of the anvil. Inthe devices utilized in the past, a pair of electrodes projected intothe confined space from the anvil side of the device. When a highvoltage electrical spark is discharged across such electrodes, air orother gas which may be confined between the tape and the anvil isinstantaneously heated and expanded. The force produced by the rapidexpansion of the gas against the tape causes it to be embossed orperforated in a desired manner.

it has been found that a single spark channel is limited in Width andmay develop a localized pressure against the surface of the tape. Inaddition, punching some holes, such as a quarter inch diameter hole,requires such high current sparks that very rapid die chipping andelectrode wear may result. Therefore, in certain instances, it isdesirable to utilize two or more pairs of spark electrodes adapted to besimultaneously energized in parallel discharge channels to produce amore uniform pressure over a much larger area. The gives rise to certaincontrol circuit problems, and applicant has found it necessary to inventa new and highly useful electrical control circuit for controlling thearc discharge in multiple pair spark electrodes.

Accordingly, it is an object of this invention to provide ew andimproved electrical control circuitry for controlling the electric sparkdischarge of multiple pair spark electrodes adapted for simultaneousenergization in parallel discharge channels.

More particularly, it is an object of this invention to provide suchelectrical control circuitry for multiple pair spark electrodes whichutilizes balancing reactors to equal ize the current in the paralleldischarge paths.

The above and other objects are realized in accordance with the featuresof one illustrative embodiment of the invention wherein the electricalcontrol circuit for the multiple pair electrodes comprises pluralbalancing reactors to equalize the current in the parallel dischargepath. For example, in the case of a spark discharge circuit utilizingtwo eiectrode pairs, two balancing reactors are arranged such that oneelectrode of each pair is connected to the opposite terminals of onebalancing reactor and the remaining electrode of each pair is connectedto the opposite terminals of a second balancing reactor. Each balancingreactor is provided with a center tap, with the center tap of onebalancing reactor being connected to ground and with the center tap ofthe other balancing reactor being connected through a switch to a sourceof potential such as the charged capacitor which, in turn, is returnedto ground.

Advantageously, each balancing reactor is wound on a use of multiplespark electrodes 3,.li8fi5dd Patented Mar. 5, 1%53 pulse transformercore of highly laminated steel. The physical arrangement of the twowindings on each core is designed to provide a maximum coefiicient ofcoupling and a minimum leakage reactance between the winding on one sideof the center tap and the winding on the other side of the center tap.When a spark is initiated by closing the switch, spark channels begin toform at the gaps between the electrode pairs. If the discharge currentsare exactly equal, then the balancing reactor has essentially no effecton the circuit because the magnetizing force due to the current inone-half of the winding is cancelled by the current in the opposite halfof the winding. However, if one spark channel starts to take more thanone-half of the current, then the coupling between the windings causesthe voltage across the other channel to increase and restore theequality of the two currents. As explained in greater detailhereinbelow, this principle may successfully be utilized in two or threeor four pair electrode arrangements, or if desired, in any greaternumber of electrode pair arrangements which embody the presentinvention.

Thus, it is another object of this invention to provide a new andimproved balanced reactor control circuit for controlling the sparkdischarge of a plurality of pairs of spark electrodes.

It is a further object of this invention to provide such an improvedbalanced reactor control circuit for plural pair spark electrodes whichfinds particular use in high speed spark discharge web punching orprinting apparatus.

It is a still further object of this invention to provide a balancedreactor are discharge control circuit, as above, which is characterizedby its efiiciency, its reliability, and its relative economy ofconstruction and operation.

The novel features which are characteristic of the invention are setforth with particularity in the appended claims. The invention itself,however, both as to its organization and method of operation, togetherwith further objects and advantages thereof, will best be understood byreference to the following description taken in conjunction with theaccompanying drawings in which:

FIGURE 1 is a sectional view of one illustrative embodiment of the webpunching apparatus capable of utilizing the plural spark dischargecontrol circuit of the present invention;

FIGURE 2 is a view taken substantially as shown along line 2-2 of FIGUREI particularly illustrating the plural spark discharge electrode pairsutilized in the apparatus of FiGURE 1;

FiGURE 2a is an enlarged View of the multiple elec trode pair and anvilassembly illustrating the spark discharge paths;

FIGURE 3 is a schematic diagram of an electrical control circuit for atwo electrode pair spark discharge arrangement embodying the presentinvention;

FiGURE 4 illustrates the construction of a balancing reactor suitablefor use with the control circuit of FIG- URE 3;

FIGURE 5 is an electrical schematic diagram of a three spark electrodepair arrangement embodying the present invention;

FIGURE 6 illustrates the construction of a balancing reactor suitablefor use with the control circuit of HG- URE 5;

FIGURE 7 is a simplified electrical schematic diagram of a controlcircuit for four spark electrode pairs embodying the present invention;and

FIGURE 8 is a simplified electrical schematic diagram of an alternativecontrol circuit for four spark electrode pairs embodying the presentinvention.

Referring now to the drawing, and more particularly to FIGURES l and 2thereof, there is shown one illustraport ring 44. Yoke extendingtherethrough, concentric with the die opening a sencetive. web punchingor printing apparatus adapted to be used with the multiple pair sparkdischarge control 011- cuit of the present invention. As there shown,the apparatus comprises a vertical mounting plate 1%, made from aluminumor other rigid material, which serves as a support and guide for themoving web W. Those skilled'in the art will appreciate that theweb W maybe paper, coated fabric, a plastic sheet or other material which is tobe perforated by the apparatus.

Suitable means (not shown) is provided for moving the web W upwardlyacross-the face of plate lib cppos1te the die assembly, which isindicated generally by the numeral 12. Such means may comprise part ofanother apparatus onwhich the web is being processed, e.g., a rotaryprinting press.

The anvil assembly is mounted on the other side of the plate and isdesignated generally by the numeral 14. Advantageously, the anvil maycomprise a knurled cylindrical disc 16 adapted to be driven bytherotatable shaft 1%, such that an end face of the knurled anv1l disc16 is positioned adjacent the web: W through an opening Ztlin themounting plate ill; The plural pairelectrode assembly comprising the;electrode pairs 24, 2d, and 28 is mounted on the insulator blocks 22 and3% by any suitable means, so as-to be positioned in the opening it)between the web W and the knurled anvil disc 16 in contact with thelatter. Advantageously, the insulator blocks 22 and are urged againstthe knurled anvil disc 16 by the biasedpivoted arm weights 32 and 34.

The die 36 is mounted adjacent the web W opposite the electrode andanvil assembly, and the die 36 is providedwith a suitable opening 38 inthe, face thereof to impart an. embossment or perforation in the web Wupon energization of the spark electrode pairs. The face of the anvil16' adjacent the web W serves to confine gases between the web and theanvil for imparting such embossments or perforations in the web. Thepaths of the spark discharge'at the knurled anvil surface is illustratedin FIGURE 20 by the heavy black lines.

Advantageously, the anvil 16 may be formed of any suitablenon-inflammable dielectric resinous organic ma terial since suchmaterial evaporates under the heat of the arc to provide additionalquantities of gas. However, other materials, such as ceramic, also aresatisfactory for this purpose. Obviously, the thickness of the web discmay be varied in accordance with the particular use to which theapparatus is put, and this thickness is not critical as long as thecontact face of the anvil at least partially confines gas adjacent theweb W.

Since it is essential that members in contact with the electrodeassembly be completely insulated from the rest of the apparatus,aninsert 49, made from Bakelite, or other dielectric material, isprovided for the plate Ill.

The die 36 mounted adjacent web W opposite the face of anvil 16 may bemade of any suitable heat resistant dielectric material. The die 36 hasan aperture'38 extending therethrough which determines the size of theopeningpunched through the web W. Manifestly, the opening 38 in a die 36may be formed of any suitable size depending upon the size of thedesired embossment or perforation in the web W, the function of theopening 3d being to impart physical indicia in the web W as the web isforced against it in response to the discharge of the spark electrodes.7 a

As shown in the illustrative embodiment of FIGURE 1, the die 36 may besupported within a die holder 42 in the form of a ring mounted within asupport ring 44 which, in turn, is secured to the yoke 46 by means of'the pivot pins 48. Advantageously, the die holder 42 is made from asuitable dielectric material, as is the sup- 42 is formed with anopening 50 with a 38. This opening 5%, in turn, communicates of the webwhich may be punched out during perforating operation, but, in addition,it causes the web W to run in contact with the surface of the die. Thoseskilled in the art will appreciate that the exemplary apparatusdescribed with respect to FIGURES l and 2 is merely illustrative of oneof the uses of the present invention, and that the invention is notlimited to such apparatus, but may be used with equally advantageousresults in other types of spark discharge devices.

Reference now is made to FIGURES 3 and 4 of the drawing wherein onespark discharge control circuit embodying the present invention is shownas adapted to control the discharge of spark electrode membercomprisingtwo pairs of parallel aligned'discharge electrodes. The firstpair of spark electrodes comprises electrodes 5d and 5d, which arepositioned adjacent the anvil l6 soas to define a. spark gap vAthcrebetween. The second pair of spark electrodes comprises electrodes58 and 6h positioned adjacent theanvil 16 so as to define a spark gap Btherebetween, which spark gap is parallel to the spark gap defined byelectrodes 54 and 56.

As stated heretofore, the use of multiple electrode pairs forthe'parallel spark channels requires the use of bale ancing reactors toequalize the currents in the parallel paths. In accordance with thepresent invention, the electrodes 54 and 58 are connected to the endterminals ofi a balancing reactor 62, while the electrodes 56 and, 60are connected to the end terminals of a balancing reactor 64.Specifically, the spark electroded l is connected to the terminal d6 ofbalancing reactor 62 and the spark electrode 58 of the other parallelpair is connected to the end terminal 68 of balancing reactor 62. Acenter tap connection 70 on balancing reactor 62 is connected by theline 72 to a contact 74 of a power switch 76, the armature 78 of whichis connected to a source of potential 80. In addition, the switcharmature 78 is connected to a capacitor 82, which, in turn, is connectedto ground. The spark electrode 56 is connected to the end terminal 84 ofbalancing reactor 64, While the spark electrode 60 is connected to endterminal 86 of balancing reactor 64. The center tap 88 on the balancingreactor 64 is connected to ground to complete the spark energizationcircuit.

The physical construction for one illustrative embodiment of balancingreactor which advantageously may be used with the invention is shown inFIGURE 4 ofthe drawing. In this embodiment, the balancing reactor 62comprises a pair of oppositely wound windings on a pulse transformercore 9il,,which preferably is formed of finely laminated steel. Asshown, the core 90 may be C-shaped with an air gap 92 between theclosely spaced ends of the core. This air gap serves to reduce theremanence induction oil the core so as to minimize the probability ofrepeating the. single channel spark. The physical arrangement of the twowindings on the core 90 advantageously provides maximum co-efiicient ofcoupling and minimum leakage reactance etween the winding on one side ofthe center tap 7t and the winding on the other side of the a center tap'79.

It now will be understood by those skilled in the art that in theoperation of the invention, the spark is initiated by closing contacts74 and 78 of switch 76 to provide a tube '52 connected to a source ofvacuum. The vacuum a connection not only serves to carry away thoseportions voltage across the spark electrodes. At this time, parallelspark channels start to form at the spark gaps A and B between theparallel pairs of spark electrodes. If the spark discharge'currents areexactly equal, the balancing reactors have essentially no effect on thedischarge circuit because the magnetizing force due to the current howin one-half winding in each balancing reactor is cancelled by thecurrent rlow in the opposite half winding of the balancing reactor.However, in accordance with 'the invention, should one spark channelstart to make more than half of the current, the coupling between thewindings on the balancing reactor causes the voltage across the otherchannel to increase and thereby restore the equality of the twocurrents. In this manner, the spark discharge currents in the parallelpaths are kept equal in an automatic and self-adjusting fashion toinsure the stability and efficiency ofi the desired operation.

A spark discharge control circuit for a three-parallel channel sparkdischarge arrangement embodying the invention is illustratively shown inFIGURES and 6 of the drawing. Thus, the spark electrodes 94 and 96adjacent the anvil 16 define a spark gap therebetwee'n to form one sparkdischarge channel, the spark electrodes 93 and 19h adjacent anvil 16define a spark gap therebetween to form a second spark dischargechannel, and the spark electrodes 192 and 104 adjacent anvil 16 define aspark gap therebetween to form the third spark discharge channel.

A first balancing reactor 104 is connected to the spark electrodes 94and 102, with electrode 94 being connected to end terminal 108 ofreactor 104 and spark electrode 102 being connected to end terminal 112of reactor 104. The center tap terminal 110 of balancing reactor 104 isconnected through a second balancing reactor 1% to the spark electrode98.

Thus, the center tap 110 of reactor 104 is connected to terminal 114 ofreactor 106 and terminal 118 of reactor 1% is connected to sparkelectrode 98. In a similar fashion, the spark electrodes 96 and 104 areconnected to the reactor 122, with spark electrode 96 being connected toend terminal 126 of reactor 122 and with spark electrode Hi4 beingconnected to end terminal 130 of reactor 122. The center tap terminal128 of balancing reactor 122 is connected to end terminal 132 of afourth balancing reactor 124, with end terminal 134 of reactor 124 beingconnected to the spark electrode 100.

It will be noted with respect to the embodiment of the invention shownin FIGURE 5, that the reactor 106 is provided with an intermediate tapterminal 116 connected to reactor 106 at a point such that approximatelyone-third oh the winding lies between terminals 114 and 116, andapproximately two-thirds of the winding lies between terminals 116 and118.

The intermediate tap terminal 116 is connected to a suitable source ofpotential 126 through the switch and capacitor arrangement shown withrespect to FIGURE 3 of the drawing. Similarly, the intermediate tapterminal 136 of reactor 124 is connected such that one-third of thereactor winding lies between terminal 134 and 136, and approximatelytwo-thirds of the reactor winding lies between terminal 136 and 132. Theintermediate tap terminal 136 is connected to ground to complete thedischarge control circuit.

As explained hereinbelow, approximately two-thirds of the reactorcurrent flows between the intermediate tap terminal 116 and the endterminal 114 of reactor 1%, and approximately two-thirds of the reactorcurrent flows between the intermediate tap terminal 136 and end terminal13 of reactor 124. In the physical construction of a reactor 166, it hasbeen found advantageous to utilize a three-layer winding as shown inFIGURE 6 of the drawing. The innermost layer 144 and the outermost layer142 are wound on the core 133 in one direction and are connected inparallel. These two windings constitute the leg of the reactor betweenthe terminals 116 and 11%. The middle layer 140 constitutes the leg ofthe reactor betweenterminals 114 and 116 and advantageously, this layeris wound in a direction opposite to that of the other two layers. Inorder to optimize the coupling, the middle layer Mil advantageously isWound from a double width conductor so that even though only one-halfthe number of turns is present, the physical length oi the winding isthe same as the inner and outer layers. This also serves to minimize theuncoupled leakage flux.

In the operation of the circuit shown in FIGURE 5 of the drawing,current I entering reactor 1'36 at the intermediate terminal lid dividesto flow in both the left and right windings. As stated above, thewinding be tween terminals 116 and 1 18 is provided with twice as manyturns as the Winding between terminals 114 and 116. Hence, when theformer winding carries half the current that is carried by the latterwinding, the net magnetization or" the core of reactor 1% is zero, andthe reactive drop of the current pulse in the winding also is zero. Thecurrent thus divides so that one-third of the I current goes to theelectrode 98, and two-thirds of the I current goes to the center tap litof reactor Hi4. Reactor ltM, divides this current equally so thatone-third of the I current goes to electrode 94- and the remainingone-third of the I current goes to the electrode 1&2.

A similar arrangement of balancing reactors 122 and 124 is used withelectrodes 96, 60 and 104 to insure that equal current will flow acrossthe spark gap between the spark electrodes. In this manner, the sparkdischarge current is maintained equalized in an automatic andself-correcting fashion in the event the voltage across one pair ofelectrodes should tend to increase or decrease with respect to thevoltage across the remaining spark electrode pairs.

FIGURES 7 and 8 of the drawing illustrate spark discharge controlcircuits embodying the invention suitable for use with four parallelspark channels. in the illustrative embodiment of FIGURE 7, the controlcircuit comprises six balancing reactors connected such that the currenthow in the discharge channels will be equalized to insure efficient andreliable operation.

Thus, as shown in FIGURE 7, the four parallel spark discharge channelsinclude the electrode pairs 15% and 152', 154- and 156, 158 and 16d, and162 and 164. Electrodes 15d and 1&2 are connected to the opposite endterminals 165 and 163 of a balancing reactor 1'76. Electrodes 154 and158 are connected to the opposite end terminals 172 and 174 of abalancing reactor 176. A center tap terminal 173 on reactor 17!) isconnected to a center tap terminal 189 on reactor 176 by means of afurther balancing reactor 132. The center tap terminal 184- on reactor182 is connected to a suitable source or" Voltage through suitableswitch and capacitive circuitry as above described.

In a similar manner, electrodes 152 and 164 are connected to theopposite end terminals 186 and 182; of a balancing reactor 1%.Electrodes 156 and 169 are connected to the opposite end terminals 1%.and 194 of a balancing reactor 2%. The center tap terminal 196 ofreactor 294 is connected to the center tap terminal 198 of reactor 2%through the windings of the balancing reactor The center tap terminal292 of reactor 2% is connected to ground to complete the spark dischargecontrol circuit.

Those skilled in the art will appreciate that the anal discharge controlcircuit shown in FIGURE 7 o insure equal current flow in each of thefour parallel spark discharge channels. It further will be appreciatedthat the current flow in the balancing reactors will be divided equallyto maintain the desired balanced condition.

An alternative embodiment of spark discharge control circuit for a fourdischarge channel arrangement is shown in FIGURE 8 of the drawing. Thespark electrode pairs comprise electrodes 2% and 21h, and 2E4, 216 and215. and 22d and 222. As explained heretofore, each of the sparkelectrode pairs define an air gap or spark channel therebetween, saidspark channels being aligned in parallel with each other adjacent theanvil (not shown.)

Spark electrodes 2% and 212 are connected to the opposite end terminals226 and 228 of balancing reactor 224. Spark electrodes 2% and 220 areconnected to the opposite end terminals 234 and 236 of balancing reactor232. The center tap terminal 2% of reactor 224 is connected to the endterminal 242 of balancing reactor 240, While the center tap terminal 233of reactor 232 is connected to the end terminal 246 of reactor 24%. Thecenter tap terminal 244 of reactor 249 is connected to a source ofpotential at the terminal 243, which in turn is trodes,

s ream.

7- connected to the appropriate switch and capacitance means of the typedescribed hereinabove.

In a symmetrical fashion, spark electrodes 21dand 214 are connected tothe opposite end terminals 252 and 254 of balancing reactor 25%. Sparkelectrodes 218 and 222 are connected to the opposite end terminals 26%and 262 of balancing reactor 258. The center tap terminal 256 of reactor25a is connected to the end terminal 268 of reactor 266 while the centertap terminal 264 of reactor 258 is connected to the end terminal 27% ofreactor 266. The center tap terminal 272 of balancing reactor 266 isreturned at the terminal 274 to the potential source to completethespark discharge control circuit.

Those skilled in the art will appreciate the operation of the circuitshown in FlGURE v8 of the drawing. Due to the symmetrical arrangement ofthe various balancing reactors forming the circuit, thecircuit serves tobalance out any inequality in current flow across the parallel dischargechannels. Thus, should the voltage at the discharge channel tend torise, the balancing reactors eiiect an opposite condition to reassertequality of the voltages :at th e variousdischarge channels. In thismanner, all of the multiple sparkelectrodes discharge channels may besimultaneously energized, and still maintain equalized currents in theparallel discharge paths.

While the various balancing reactors shown in the drawing and describedhereinabove may take any suitable dorm, in practice it has been foundadvantageous to utilize balancing reactors having the followingcharacteristics. It is highly-desirable that theco-eflicien-t ofcoupling between the winding on one-half of the reactor and the windingon the other half of the reactor be as high as possible. In other words,magnetic flux which links onehalf of the winding should, as far aspossible, link the other half of the winding. Any flux which linkspartof the turns but does not link all of the turns of both windings isdesignated as leakage flux since it is not cancelled out by the oppositemagnetomotive forces.

It alsois important that the inductance of the winding as measuredacross the reactor be as high as possible in order to maximizethe-transformer action between the two halves of the reactor winding. Itfurther has been found in the practice of the invention that the steelcore of the reactor advantageously should be of thin laminations, suchas one mil, to permit flux penetration into the steel at frequencies ofmany megacycles, since the frequency components involved in theoperation of the reactor are very high, and substantial changes incurrents occur in time intervals of a few thousandths of a microsecond.(Ferrite cores have been used for this purpose, but they are lessdesirable than finely laminated steel cores because the ferritematerials saturate at a lower flux density and have lower permeability.

In one practical embodiment of the invention, which has been used withgreat success, reactors have been utilized having a measured inductancefor each half winding of approximately SOD-1,000 microhenries. In suchreactors, the magnitude of the leakage inductance has been found to betypically about 0.2 microhenry.

While there has been shown and described a specific embodiment of thepresent invention, it will, of course, be understood that variousmodifications and alternative constructions may be made withoutdeparting from the true spirit and scope of the invention. Therefore, itis in tended by the appended claims to cover all such modifications andalternative constructions as fall within their true spirit and scope.

What is claimed as the invention is:

1. The improvement of spark discharge control means comprising thecombination of a plurality of parallel aligned pairs of sparkelectrodes, said spark electrodes defining a plurality of parallel sparkdischarge channels, a source of potential of magnitude sufficient toenable a spark discharge to take place in each pair of spark elecaplurality of balancing reactors, each comprising reactor. windingshaving end terminals and an intermediate tap terminal, circuit meansconnecting each of said spark electrodes to a different end terminal ofsaid reactor windings, and circuit means connecting the intermediate tapterminals of the balancing reactors to said source of potential forsimultaneous energization of said spark electrodes such that anydifference in potential across said spark electrode pairs is balanced bysaid control means to equalize the current flows in said electrodepairs, 7

2. Theimprovement of spark discharge control means comprising thecombination of two pairs of parallel aligned spark electrodes, saidspark electrodes defining two parallel spark discharge channels, asource of potential of magnitude sufficient to enable a spark dischargeto take-place'in said pairs of sparkelectrodes, a pair of balancingreactors, eachcomprising reactor windings having end terminals; and acenter tap terminal, first circuit meansconnecting each of said sparkelectrodes to addferent end terminal of said reactor windings, andsecond circuit means-connecting the center tap terminals of thebalancing reactors to said source of potential forsimultaneousenergization ofsaid spark electrodes such-that anydifferencein potential across said spark electrode pairs is-balancedby saidcontrol means to equalize the current flows in said electrode pairs.

3. The improvementot spark dis harge control means in accordance withclaim 2 wherein each of said reactors comprises a laminated steel corehaving a pair of windings connected at said center t-ap terminal, saidwindings being wound in opposite directions on said core.

4. The improvement of spark discharge control means in accordance withclaim 2 wherein said second circuit means comprises-a power switch andstorage capacitor means connected to saidpower switch for applyingenergizing potential. to said balancing reactors upon closing of saidpower switch.

5. The improvement of spark discharge control means comprising thecombination of three pairs of parallel aligned spark electrodes, saidspark electrodes defining threeparallel spark discharge channels, asource of potential of magnitude sutficient to enable a spark dischargeto take place in each pair of spark electnodes, a plurality of balancingreactors, each comprising reactor windings having end terminals and anintermediate t-ap terminal, circuit means connecting each of said sparkelectrodes to a diiierent end terminal of said reactor windings, andcircuit means connecting the intermediate tap terminals of the balancingreactors to said source of potential for simultaneous energization ofsaid spark electrodes such that any difference in potential across saidspark electrode pairs is balanced by said control means to equalize thecurrent flows in said electrode pairs.

6. The improvement of spark discharge control means comprising thecombination of three pairs of parallel aligned spark electrodes, saidspark electrodes defining three parallel spark discharge channels, asource of potential of magnitude sufficient to enable a spark dischargeto take place in each pair of spark electrodes, four balancing reactors,each comprising reactor windingshaving end terminals and an intermediatetap terminal, circuitmeans connecting the four spark electrodes in two aof said electrode pairs to a different end terminal of the reactorwindings of two balancing reactors, circuit means connecting each of theremaining two balancing reactors betWeen t-he center tap terminals ofthe first two balancing reactors and a spark electrode of the remainingelectrode pair, circuit means connecting the intermediate tap terminalsof said remaining two balancing reactors to said source of potential forsimultaneous energization of said spark electrodes such that anydifference in potential across said spark electrode pairs is balanced bysaid control means to equalize the current flows in said electrodepairs. 7

7. The improvement of spark discharge control means in accordance withclaim 6 wherein said intermediate tap terminals of said remaining twobalancing reactors is connected to the reactor windings of the lattersuch that onethird of each reactor winding lies between one end terminaland the intermediate tap terminal and two-thirds of each reactor windinglies between the other end terminal and the intermediate tap terminal.

8. The improvement of spark discharge control means in accordance withclaim 7 wherein each of said remaining two balancing reactors comprisesa laminated steel core having three layers of windings thereon, theinnermost and outermost winding layers having equal numbers of turns,and the middle winding layer having half as many turns as the innermostand outer-most layers, and being wound in the opposite direction withrespect to said innermost and outermost layers.

9. The improvement of spark discharge control means in accordance withclaim 8 wherein the windings of said middle layer are double thediameter of the windings of said innermost and outermost layers.

10. The improvement of spark discharge control means comprising thecombination of four pairs of parallel aligned spark electrodes, saidspark electrodes defining four parallel spark discharge channels, asource of potential of magnitude sufil-cient to enable a spark dischargeto take place in each pair of spark electrodes, at least six balancingreactors, each comprising reactor windings having end terminals and acenter tap terminal, circuit means connecting each of said sparkelectrodes to a difierent end terminal of said reactor windings, andcircuit means connecting the center tap terminals of the balancingreactors to said source of potential for simultaneous energization ofsaid spark electrodes such that any diiference in potential across saidspark electrode pairs is balanced by said control means to equalize thecurrent flows in said electrode pairs.

11. The improvement of spark discharge control means comp-rising thecombination of four pairs of parallel aligned spark electrodes, saidspark electrodes defining four parallel spark discharge channels, asource of poten- 40 tial of magnitude sufiicient to enable a sparkdischarge to take place in each pair of spark electrodes, six balancingreactors, each comprising reactor windings having end terminals and acenter tap terminal, circuit mean-s connecting the spark electrodes oftwo of said pairs to a different end terminal of two of said reactorwindings, circuit means connecting the spark electrodes of the remainingtwo pairs to a diflerent end terminal of two other reactor windings,circuit means connecting the remaining two reactor windings between thecenter tap terminals of the first four reactor windings, and circuitmeans connecting the center tap terminals of said remaining two reactorwindings to said source of potential for simultaneous energization ofsaid spark electrodes such that any difference in potential across saidspark electrode pairs is balanced by said control means to equalize thecurrent flows in said electrode pairs.

12. The improvement of spark discharge control means comprising thecombination of four pairs of parallel aligned spark electrodes, saidspark electrodes defining four parallel spark discharge channels, asource of potential of magnitude sufiicient to enable the sparkdischarge to take place in each pair of spark electrodes, three pairs ofbalancing reactors, each comprising reactor windings having endterminals and a center tap terminal, circuit means connecting two pairsof said spark electrodes to a diiferent end terminal of one pair ofbalancing reactors, circuit means connecting the remaining two pairs ofspark electrodes to a different end terminal of a second pair ofbalancing reactors, circuit means connecting the third pair of balancingreactors between the center tap terminals of the first and second pairof balancing reactors, and circuit means connecting the center tapterminals of the third pair of balancing reactors to said source ofpotential for simultaneous energization of said spark electrodes suchthat any difference in potential across said spark electrode pairs isbalanced by said control means to equalize the current flows in saidelectrode pairs.

No references cited.

1. THE IMPROVEMENT OF SPARK DISCHARGE CONTROL MEANS COMPRISING THECOMBINATION OF A PLURALITY OF PARALLEL ALIGNED PAIRS OF SPARKELECTRODES, SAID SPARK ELECTRODES DEFINING A PLURALITY OF PARALLEL SPARKDISCHARGE CHANNELS, A SOURCE OF POTENTIAL OF MAGNITUDE SUFFICIENT TOENABLE A SPARK DISCHARGE TO TAKE PLACE IN EACH PAIR OF SPARK ELECTRODES,A PLURALITY OF BALANCING REACTORS, EACH COMPRISING REACTOR WINDINGSHAVING END TERMINALS AND AN INTERMEDIATE TAP TERMINAL, CIRCUIT MEANSCONNECTING EACH OF SAID SPARK ELECTRODES TO A DIFFERENT END TERMINAL OFSAID REACTOR WINDINGS, AND CIRCUIT MEANS CONNECTING THE INTERMEDIATE TAPTERMINALS OF THE BALANCING REACTORS TO SAID SOURCE OF POTENTIAL FORSIMULTANEOUS ENERGIZATION OF SAID SPARK ELECTRODES SUCH THAT ANYDIFFERENCE IN POTENTIAL ACROSS SAID SPARK ELECTRODE PAIRS IS BALANCED BYSAID CONTROL MEANS TO EQUALIZE THE CURRENT FLOWS IN SAID ELECTRODEPAIRS.